Inter-Cell Interference
Inter-cell interference (ICI) can be the primary limiting factor on the performance of cellular networks. If mobile stations (MSs) located at edges of adjacent cells served by different base stations (BSs) use the same time and frequency resource to transmit data, then the MSs are subject to possible ICI. It is important that BSs have some methods for coordinating the allocation of frequency resources so that network performance is optimized.
Partial Frequency Reuse
Partial frequency reuse (PFR) can reduce ICI. Given all the available frequency resources in the network, PFR partitions the resources into disjoint set, and allocates the resources for use by MSs at in cell centers or in sectors at the edges of the cells.
With PFR, the MSs in adjacent cell edge sectors transmit using different frequency resources. Conventional PFR methods are fixed over time. The MSs in a particular sector of the cell must communicate with the BS using the frequency resources allocated for the sector.
While PFR is effective in reducing ICI, PFR decreases frequency diversity, because the MSs can only use a small part of the overall frequency spectrum. This implies that the MSs have less choice to send or receive data through frequency resource with good channel condition, thus restricting a maximum rate at which the BS and MSs can communicate.
Other forms of coordination requires centralized scheduling amongst the cells, which is very difficult to realize in practice given the vast amount of information that needs to be communicated with the centralized scheduler.
Therefore, there is a need to reduce ICI in a dynamic and flexible manner so that frequency diversity can be attained with minimal overhead.